Publication details
Shear failure of rocks and creating their shear plane
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| Year of publication | 2015 |
| Type | Conference abstract |
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| Description | The study was focused on exploration of the shear strength of slate with distinguish planes of weakness, i.e. cleavage. Slaty cleavage represents the ability of rock to split into more or less parallel planes and disturbs the rock massif. The presence of these planes of weakness affects the strength and deformational behaviors of rocks and indicates asymmetric fracture of rocks and unpredictable strength behaviour. Tests were carried out on the laminated slate with predetermined shear plane. This rock originates from „Bělá” quarry from the Moravo-Silesian Culm, Czech Republic. The oriented specimens were taken by manual drilling machine. The drilled specimens of slate were divided into five groups based on the different angle between shear plane and cleavage. Testing of each group was carried out in seven directions with an interval of 15°. The first direction which was called “zero” direction was perpendicular to the cleavage. Solids were tested at portable rock shear box assembly Matest A129. Specimens confirmed anisotropic strength behaviour. Large variability of measured values of the strength was caused mainly by various dip of cleavage and by the direction of shear but in lesser extent. Two types of mechanisms of shear failure of specimens and creating their shear planes were distinguished (sliding vs. splitting). The first type was recognized for groups 1 a 2. These groups were characterized by lower values of shear strength and smoothed newly-formed shear planes, which are parallel to cleavage. It might have been caused by the parallel position of phylosilicates. These minerals reduce the friction ability of rocks and allow them to split. The other type, splitting, was recognised for group 4. This group was characterized by high values of shear strength without visible newly-formed shear planes and the specimens were crushed during the test. It might be explained by dominant influence of friction ability of rock. The group 3 is considered to be a transitional group with lower values of shear strength and specimens were crushed during testing. Significant effect of the shear direction on the strength was demonstrated on the group 5, on the specimens with cleavage upright to the shear plane. |